A013

Diagnostic Chart:

CIRCUIT DESCRIPTION
The in-car temperature sensor is a thermistor that controls the signal voltage to the ACP The ACP applies a voltage on CKT 734 to the sensor. When the sensor is cold its resistance is high, therefore, the ACP will see a high signal voltage. As the sensor warms, its resistance becomes less and the signal voltage is pulled low through the sensor ground, CKT 407. This signal voltage will vary between 5V (open circuit) and 0V (short circuit).

TEST CONDITION(S)
1. Ignition "ON."
2. Outside air temperature reads above -20°F.

FAILURE CONDITION(S)
The signal voltages indicates less than -34°C (open circuit) or greater than 99°C (short circuit).

ACTION TAKEN
1. A substitute temperature reading will be used to allow continued climate control operation.
2. The in-car temperature reading AD25 will display the actual sensor reading.

NOTES ON FAULT TREE
1. ACP data value AD25 displays in-car temperature. The valid operating range is from -34°C to 9°C.
2. A reading too low indicates an open circuit. Jumpering the harness connector will determine whether the wiring or sensor is the cause of the open.
3. A reading too HI indicates a short circuit. Removing the sensor will determine whether the wiring or sensor is the cause of the short.
4. The open has been determined to be in the wiring. Proviing a ground at the jumper will determine if the open is in the ground wiring or the sensing wire.
5. Grounding the connector at the ACP will determine if the open is in the sense circuit or at the ACP connection/ACP internal.
6. Note values of AD25, AD26, AD27, and AD28. If all read near -40 repair open CKT 407 between ACP and C201 "D." If AD25 and AD26 read near -40 repair open CKT 407 between C201 "D" and 5241. If only AD25 reads near -40 repair open CKT 407 between 5241 and In-Car sensor.

NOTES ON INTERMITTENTS
On some early production vehicles (AD99 ="8640" this code may set intermittently if sensor temperature false below -20°F. The code will become history after sensor temperature increases.

If an intermittent code A013 is being set, Select ACP Snapshot Data for Code A013 and note value of AD25. A reaing of approximately -40 indicates an intermittent open, a reading above 99 indicates an intermittent short.

Manipulate the related wiring while observing ACP data AD25. If the failure is induce, the reading will jump outside its normal range.

If the value displayed by AD25 is not reasonably close to the actual temperature of the air at the sensor, check for proper terminal contact, proper air flow across the sensor, or replace the sensor.